Ignition system



y 1 ,1 T. F. ROBINSON ETAL 2,376;l 89

IGNITION SYSTEM Filed April 26, 1945 Inventors: Thomas F? Robinson,

Re2ina1d. T Coe, Douglas P. Welch,

TheirAttorney.

Patented May 15,1945

Thomas F. Robinson, Kenilworth, and Reginald T. (Joe and Douglas F. Welch, Rugby, England, assignors to General Electric Company, 'a cornotation of NewYork Application April 26, 1942, Serial No. 484,582

' I In Great Britain May 18, 1942 8 Claims. (c sis-213) Our invention relates .to ignition systems for internal combustion engines of the type in'which the, ignition current is generated and distributed I at relatively low voltages and is transformed to the requisite high voltage for supply to the spark plugs by individual high voltage transformers for each spark plug. These high tension transformers may be located at the plugs or in the circuits between the distributor and the plugs.

An object of our invention is to provide an improved low voltage ignition system for eflicient operation at widely different altitudes.

Another object of our invention is to provide an improved ignition system utilizing a high frequency oscillation'discharge circuit provided with a spark gap and means for stabilizing the discharge of the spark gap including a resistance value of this resistance may be of the one-half a megohm and may convenie tly be,

capacity. In order to stabilize.'tlie breakdown value of the series spark gap, a resistance of predetermined value is permanently connected across the spark plug connected to the g p. .The der of included in the spark plu insulator or may be connected across "the electrodes and outside of the spark plug. 7 Preferab y a series impedance also is included in the lead from the higlrvolt- -'age capacitance to the spark plug in order to .limitthe current flowing to the plug tojminimize the erosion of' the'spark plug electrode,

' may be replaced by connected across-the spark plugs of the system.

Further objects and advantages of our invention will become apparent and our invention will bebetter understood from the following description referring to the accompanying drawing, and the features of novelty which characterize our invention will be pointed out with particularity inathe claims annexed to and forming part of this specification; 1 v

The drawing schematically illustrates an ignition system provided with an embodiment of our invention.

In a low tension ignition system, it hasbeen found desirable to provide for the discharge of the'spark plugs at a relatively high frequency I of a value between 0.5 to 'meg'acycles. Under such high frequencies, therapidrate of voltage rise across the spark plug discharge electrodes provides a suflicient breakdown or sparking voltage evenwhen the plug is heavily fouled by. a

' leakage resistance across the spark plug gap. of, the order 'of 1000 ohms. A- high frequency impulse or oscillation may be generated by the, .sudden' discharge of a relatively small highvolt-' age capacitance, preferably having a capacity' greater than that of the spark plug andIits assoa high tension transformer. The discharge is effected at a, predetermined voltage by the breakdown of a spark gap connected in series with the high voltage end of the high voltage capacipoints; inductance may have a value of a few microhenries and may be located on either side of the series spark gap. This inductance a series resistance; although an inductance is preferable.

Referring to the drawing, I have shown a low voltage ignition system in whichva condenser .HI

is adapted to be connected by an ignition switch ll across a su'itablegsource of alternating current electrical power supply l2, such as a magneto,

. through a circuit breaker [3 arranged to be operated by asuitable cam M which is'actuated at a predetermined relative speed to thevspeed of the engine and the frequency of the altemat-- ciated circuit, connected across the secondary of a tance and with the central'spark plug discharge electrode. This spark gap preferably is of .the

enclosed pressure gas filled type to provide a quenched spark gap. The voltage across the spark plug gap-is partly determined by the volt- 'age breakdown of the series spark gap and the electrical constants of'the' high voltage, capaci tance and the spark plug circuit inductanceand ing'current supplied by the source I2; This pro-. vides for alternately charging the condenser ill to oppositepolaritie by the voltage across the source 12 and subsequently discharging the condenser in through an ignition circuit which in cludes a circuit'breaker lboperated by a cam' It at a predetermined speed and, angular position relative to the breaker-cam H, such that when the condenser 10 discharges, thecircuit breaker I5 is closed and the circuit breaker I is opened, thereby providing for the discharge of the cone denser l0 thrOughQan ignition distribution circuit to engine spark plugs. Thecircuit breaker II connects the condenser In to a distributor including a distributor arm l1 operated at a pre determined speed relative to the cams l l-and 16 to provide for the sequential distribution oi ignition voltage to a plurality of distributor electrode contacts t8; Eachof these vdistributor electrode contacts I8 is adapted to be connected to a distribution. circuit which includes a transformer having a primary winding la and a secondary winding 20. The distribution voltage to the transformer primary winding is is of the order of 200 volts.

The desired high frequency impulse is gen-- erated in Ian-oscillatory circuit by the sudden discharge of a condenser 2| .co 'transfom ersecondary winding I and takes place ected across the when the voltage across the condenser 2! has built up to a value suflicient to cause breakdown in a discharge path including a, spark gap 22 preferably formed in a quenched spark gap device 23 connected in series with a current limiting inductance 24 and the discharge electrodes 25 and 26 of a spark plug. A stabilizing resistance 21 is connected across the spark plug electrodes 25 and 28 and a. capacitor 28 is also connected across the spark plug electrodes 25 and 26. The ar rangement of the capacitor 28 and resistance 21 across the spark plug electrodes 25 and 26 assures that the discharge circuit including the spark plug will be at substantially ground potential whenever voltage is applied to the transformer primary winding it. In order to minimize electrical interference with other equipment adjacent the ignition system, a metal casing til is arranged about the transformer windings it and 2d, the

condenser ill, the spark gap device and the inductance iii which form the oscillatory electrical circuit, and this casing 29 is connected to ground in any suitable manner, as by a conductor 36.

While we have described a particular embodiment of our invention, modification thereof will occur to those skilled in the art. We desire it to be understood, therefore, that our invention is not limited to the particular arrangement disclosed, and we intend in the appended claims to cover all modifications which do not depart from the spirit and scope of our invention.

What We claim as new and desire to secure by Letters Patent of the United States, is:

1. An ignition system having means including a quenched spark gap for producing high frequency electrical oscillations, a spark plug connected to said high frequency oscillation produclng means, and means including a resistor of predetermined value connected across said spark plug for stabilizing the operation of said quenched spark gap.

, 2. An ignition system including a source of electricalvoltage, an oscillating high frequency circuit including a quenched spark gap connected to said source of electrical voltage, a spark plug connected to said high frequency circuit, a capacitor connected across said spark plug, and a resistor of predetermined value connected across said spark plug for stabilizing the operation of said quenched spark gap.

3. An ignition system including a source of electrical voltage, a transformer having a primary winding connected to said source of electrical voltage and a, secondary winding, means including a capacitor connected across said transformer secondary winding and a quenched spark gap connected tosald transformer secondary winding for providing a high frequency oscillating circuit, a spark plug connected to said spark gap, and a resistor connected across said spark plug for stabilizing the operation of said quenched spark gap.

4. An ignition system including a, source of electrical voltage, a transformer having a primary winding connected to said source of electrical voltage and a secondary winding, means including a first capacitor connected across said transformer secondary winding and a spark gap connected to said transformer secondary winding for providing a high frequency oscillating circuit,

a spark plug connected to said spark gap, a sec- 0nd capacitor connected across said spark plug, and a resistor connected across said spark plug for stabilizing the operation of said spark gap.

5. An ignition system includinga source of electrical voltage, a transformer having a primary winding connected to said source of electrical voltage and a secondary winding, means including a capacitor connected across said transformer secondary winding and a quenched spark gap connected to said transformer secondary winding for providing a high frequency oscillating circuit, an inductance connected in series with said quenched spark gap, a spark plug connected to said inductance, and a resistor connected across said spark plug for stabilizing the operation of said quenched spark gap.

5. An ignition system including a source of electrical voltage, a transformer having a primary winding connected to said source of electrical voltageand a secondary winding, means including a first capacitor connected across said transformer secondary winding and aquenched spark gap connected to said transformer secondary winding for providing a high frequency oscillating circuit, an inductance connected in series with said quenched spark gap, a spark plug connected to said inductance, a second capacitor connected across saidspark plug, and a resistor connected across said spark plug for stabilizing the operation of said quenched spark gap.

7. An ignition system including a source of electrical voltage, a transformer having a primary winding connected to said source of electrical voltage and a secondary winding, means including a. capacitor connected across said transformer secondary Winding and a, spark gap connected to said transformer secondary winding for providing a high frequency oscillating circuit, an inductance connected in series with said spark gap, a spark plug connected to said inductance, a resistor connected across said spark plug for stabilizing the operation of said spark gap, and a grounded shielding casing arranged about said transformer, capacitor, spark gap, and inductance.

8. An ignition system including a source of electrical voltage, a transformer having a primary winding connected to said source of electrical voltage and a secondary winding, means including a first capacitor connected across said transformer secondary winding and a quenched spark gap connected to said transformer secondary winding for providing a high frequency oscillating circuit, an inductance connected in series with said quenched spark gap, a spark plug connected to said inductance, a second capacitor connected across said spark plug, a resistor connected across'said spark plug for stabilizing the operation of said quenched spark gap, and a grounded shielding casing arranged about said transformer, first capacitor, spark gap, and in- 

